AIR-BREATHERS 12 
Go 
6 to 8mm. in diameter. It has four whorls, a large 
umbilicus, a circular aperture, and many low cross- 
ribs. Variety cronkheiter, Newe., is a little convex 
above, and the whorls are almost channeled; dia- 
meter 5mm. From Alaska and Oregon, also north- 
ern California. 
Oreohélix strigosa, Gld., the 
Mountain Snail, (Patula strigo- 
sa), 1s the most abundant snail 
found between the Rocky Moun- 
tains and the Sierra Nevada 
range. It assumes very many 
forms, one of which is well shown in Figure 103. 
It abounds especially in Idaho and Utah, and 
some varieties are found far up on mountain sides, 
even as high as 8,500 feet. The shell has a broad 
umbilicus, a nearly circular aperture, and a sharp 
lip. The whorls are about five in number, and in 
most specimens the spire is low. The average di- 
ameter is rather less than an inch, though some 
varieties are much smaller. 
Fig. 103 
Perhaps no shell in the country has so many 
varieties as this mountain snail. Some are al- 
most smooth, some ribbed spirally, others trans- 
versely. Some are nearly white, others marked 
with brown stripes. Very many of the varieties 
have received names, such as cooperi, hemphilli, 
gouldi, castanea, and multicostata, but it would 
be out of place in this small volume to attempt to 
describe them all. One of the most marked varie- 
ties, which we shall even consider as a distinct 
